Interpolation circuitry is commonly employed in incremental and absolute digital motion encoding systems, where the interpolation circuitry is configured to generate digital pulses having higher frequencies than base sinusoidal analog signals input to the circuitry. As the interpolation factor of the circuitry increases, the accuracy of the interpolation circuitry becomes ever more critical since the output provided by such circuitry ultimately determines the accuracy of the encoding system. Unfortunately, due to the architecture of most interpolation circuitry—which typically relies on a large number of comparators—the outputs provided by interpolation circuitry tend to be noisy and contain undesired noise spikes arising from excessive switching in the comparators. As a result, the comparators employed in interpolation circuitry for motion encoders typically employ a significant amount of hysteresis to provide immunity from noise spikes. Such hysteresis itself becomes a source of inaccuracy for the interpolation circuitry, however, especially at high interpolation factors.
What is needed is interpolation circuitry for motion encoding systems that features improved immunity from noise, is capable of providing high interpolation factors, and that can provide highly accurate interpolation output signals.